// adds requestAnimationFrame functionality
// Source: http://strd6.com/2011/05/better-window-requestanimationframe-shim/

window.requestAnimationFrame || (window.requestAnimationFrame =
  window.webkitRequestAnimationFrame ||
  window.mozRequestAnimationFrame    ||
  window.oRequestAnimationFrame      ||
  window.msRequestAnimationFrame     ||
  function(callback, element) {
    return window.setTimeout(function() {
      callback(+new Date());
  }, 1000 / 60);
});
